This invention relates to a device for use in downhole drilling, and in particular to a downhole device for use when drilling an oil or gas well.
During the drilling of oil or gas wells, problems often arise because of differences in the pressures in the geological formation being drilled and at the surface, or between the pressure of the drilling mud and the formation pressure. Three major problems of this type include blowouts, differential sticking and mud circulation loss. Any of these problems can be extremely dangerous, and often require expensive solutions.